The U.S. Environmental Protection Agency has re-evaluated the current science on fluoride and is taking steps to begin a phased-down withdrawal of the pesticide sulfuryl fluoride, a pesticide that breaks down into fluoride and is commonly used in food storage and processing facilities. Sulfuryl fluoride is currently registered for the control of insect pests in stored grains, dried fruits, tree nuts, coffee and cocoa beans, and for use in food handling and processing facilities. Although sulfuryl fluoride residues in food contribute only a very small portion of total exposure to fluoride, when combined with other fluoride exposure pathways, including drinking water and toothpaste, EPA has concluded that the tolerance (legal residue limits on food) no longer meets the safety standard under the Federal Food, Drug, and Cosmetic Act (FFDCA) and the tolerances for sulfuryl fluoride should be withdrawn.

Sulfuryl fluoride is an important replacement for several post-harvest uses of the stratospheric ozone-depleting pesticide, methyl bromide. Methyl bromide has been phased-out in developed countries under the Montreal Protocol, and many industries that previously relied on methyl bromide to control insect pests in stored and processed food commodities and in food processing and handling facilities now depend on sulfuryl fluoride. Since sulfuryl fluoride is an important alternative to the ozone depleting pesticide methyl bromide, EPA is proposing to phase out uses of sulfuryl fluoride over a period of three years. EPA is working to identify potential alternatives.

OPP’s Assessment for Sulfuryl Fluoride and its Breakdown Product, Fluoride

OPP completed its updated assessment of the risks of sulfuryl fluoride, focusing on the risks of fluoride. OPP’s assessment is consistent with and relies heavily on the peer-reviewed Fluoride Dose Response and Relative Source Contribution documents developed by EPA’s Office of Water (OW).

In their review of fluoride in drinking water released March 2006, the National Research Council (NRC) of the National Academies of Science (NAS) recommended that EPA update its fluoride risk assessment to include new data on health risks and better estimates of total exposure. To address these recommendations, EPA’s Office of Water has completed new assessments that consider health effects data on skeletal and dental fluorosis and also update exposure estimates to reflect current conditions. OPP has built upon the work of OW by updating its human health risk assessment for sulfuryl fluoride based on the new OW dose-response and relative source contribution documents and using the more sensitive health endpoint of severe dental fluorosis, as recommended by the NRC.

OPP’s revised sulfuryl fluoride human health risk assessment shows that aggregate fluoride exposure is too high for certain identifiable subpopulations in the United States, in particular children under the age of 7 who live in areas with higher fluoride concentrations in drinking water resulting from natural background sources. OPP stresses that the assessment does NOT indicate that the majority of the U.S. population is receiving excessive exposure to fluoride. Furthermore, fluoride exposure for a particular individual can only be determined based on that individual’s particular set of circumstances such as where they live, how much water they drink, and how much toothpaste they may swallow when brushing their teeth.

Both OW’s dose response analysis and OPP’s risk assessment evaluate the ability of fluoride to cause “severe dental fluorosis.” Dental fluorosis in the United States appears mostly in the very mild or mild form – as barely visible lacy white markings or spots on the enamel. The severe form of dental fluorosis, with staining and pitting of the tooth surface, is rare in the United States. Severe dental fluorosis is rare in the U.S. National surveys have found too few cases to provide an accurate estimate other than it is <1% for people between ages 6 and 49

Most people in the United States are not exposed to unsafe levels of fluoride. However, aggregate fluoride exposure for infants and children under the age of 7 years old, where drinking water contains high levels of natural fluoride, exceeds the level that can cause severe dental fluorosis. Sulfuryl fluoride contributes only a small amount to their overall exposure. Thus, EPA’s OPP finds that the sulfuryl fluoride tolerances do not meet the FFDCA safety standard.

Sulfuryl Fluoride Background

Sulfuryl fluoride is a fumigant that was initially registered in 1959 for control of termites in wood structures. In 2004 and 2005, EPA registered sulfuryl fluoride for control of insect pests in harvested and processed foods such as cereal grains, dried fruits, tree nuts, cocoa beans, coffee beans, and also in food handling and processing facilities.

Because sulfuryl fluoride breaks down to form fluoride when it is applied and can leave fluoride residues on treated food, EPA established maximum allowable residue limits (know as tolerances) in 2004 for fluoride on the food commodities approved for treatment with sulfuryl fluoride.

Under the Federal Food, Drug, and Cosmetic Act (FFDCA), EPA is allowed to establish and retain in effect tolerances for pesticide residues only if “aggregate exposure,” (i.e., exposures from food and other non-occupational sources such as drinking water and dental products), to major identifiable subpopulations is “safe.” FFDCA defines “safe” as “a reasonable certainty of no harm.”

In 2004, the Fluoride Action Network (FAN) filed an objection to the sulfuryl fluoride tolerances and requested a hearing. FAN’s objections rest on their belief that fluoride exposure is not safe under the FFDCA. EPA’s Office of Pesticide Programs (OPP) has updated its assessment of the risks of sulfuryl fluoride as part of its response to the FAN objections. To ensure transparency in this action, EPA is making the proposed order responding to the Fluoride Action Network’s objections, the draft assessment, and the draft impact assessments available for a 90-day public comment period. The documents are available in docket number EPA-HQ-OPP-2005-0174.